import math

def quadratic(a, b, c):
    x1 = (-b + math.sqrt( b * b - 4 * a * c)) / ( 2 * a )
    x2 = (-b - math.sqrt( b * b - 4 * a * c)) / ( 2 * a )
    return (x1 , x2)
    pass

# 测试:
print('quadratic(2, 3, 1) =', quadratic(2, 3, 1))
print('quadratic(1, 3, -4) =', quadratic(1, 3, -4))

if quadratic(2, 3, 1) != (-0.5, -1.0):
    print('测试失败')
elif quadratic(1, 3, -4) != (1.0, -4.0):
    print('测试失败')
else:
    print('测试成功')
